A Policy and Charging Rules Function (PCRF) provides a differentiated policy by subscriber to a Policy and Charging Enforcement Function (PCEF) of an IP-Edge of an access network, such as a Packet Data Network-GateWay (PDN-GW) of a Long Term Evolution (LTE) network, a Gateway GPRS Support Node (GGSN) of a High Speed Packet Access (HSPA) network, a Packet Data Serving Node (PDSN) of a Code Division Multiple Access (CDMA) network, an Access Service Network-GateWay (ASN-GW) of a mobile Worldwide Interoperability for Microwave Access (WiMAX) network, and an evolved Packet Data Gateway (ePDG) of an Interworking-Wireless Local Area Network (I-WLAN) network.
The PCRF is a device for generating a differentiated policy by subscriber. The PCRF receives Quality of Service (QoS) and billing information of a subscriber from a Subscription Profile Repository (SPR), and receives access network information from the PCEF.
The PCRF performs dynamic resource allocation based on real-time service information. For the sake of this, the PCRF receives dynamic service information from an Application Function (AF). The IP-Edge (or PCEF) transmits IP address information, which is allocated to a user terminal in the IP-Edge, together with a terminal IDentifier (ID) from the PCRF at an IP-Connectivity Access Network (IP-CAN) session generation time point. And, if receiving a service request from the user terminal, the AF makes a request which includes an IP address of the user terminal for resources necessary for service provision.
The PCRF identifies the user terminal using the IP address of the user terminal included in the service request received from the AF, determines a policy based on subscription information of the user terminal, and forwards the determined policy to the IP-Edge.
If the IP address allocated in the IP-Edge is an Internet Protocol version 4 (IPv4) address, the IP-Edge allocates a private IPv4 address instead of allocating a public IPv4 address directly to the user terminal due to an IP address exhaustion problem and a security problem. In this case, the translation of a private IP address into a public IP address is implemented through a Network Address Translation (NAT) in order to receive the provision of service from a server of an external network.
Particularly, when a network provider and a service provider are separated like a Sponsored Data Connectivity architecture defined in the 3rd Generation Partnership Project Policy and Charging Control (3GPP PCC) Release (Rel.) 10, a private IP address is allocated to a user terminal by the IP-Edge of the network provider and, for the sake of service provider's AF interworking, the private IP address is translated into a public IP address by the NAT.
However, when an IP address of the user terminal is translated by the NAT, because the AF cannot know the IP address before address translation, dynamic service information forwarded by the AF to the PCRF is based on an IP address after the address translation. In this case, because the PCRF provides a service based on IP address information of the user terminal forwarded from the IP-Edge, there is a problem that the PCRF cannot process the dynamic service information forwarded by the AF.